The invention relates to a process for double impregnation of electrical capacitors which can be employed especially for alternating voltage (50 Hz) and for direct voltage with discharge and/or with phase inversion.
The capacitors involved may have armatures which are metallized or else consisting of aluminum sheet.
U.S. Pat. No. 1,989,046 describes a process for impregnation of electrical capacitors which consists in impregnating, in a first step, windings consisting of sheets of paper and of sheets of metal with an oil which has a high dielectric constant, such as castor oil, and then, in a second step, the said suitably impregnated windings are introduced into a casing filled with a sufficient quantity of a mineral oil in order to coat the said windings completely.
The mineral oil present in the casing must have high flash and boiling points and must be chemically inert.
This procedure has the disadvantage that the two liquids can mix and thus in the long term entail a deterioration of the windings which might be only partially impregnated with the dielectric oil.
In addition, in the case of breakdown with rupture of the casing and inflammation, there is a risk of the fire being propagated by a jet of ignited liquid.